Manufacturing process for integrated computational elements

ABSTRACT

Disclosed are methods of fabricating an integrated computational element for use in an optical computing device. One method includes providing a substrate that has a first surface and a second surface substantially opposite the first surface, depositing multiple optical thin films on the first and second surfaces of the substrate via a thin film deposition process, and thereby generating a multilayer film stack device, cleaving the substrate to produce at least two optical thin film stacks, and securing one or more of the at least two optical thin film stacks to a secondary optical element for use as an integrated computational element (ICE).

BACKGROUND

The present disclosure is related to optical processing elements and, inparticular, methods of manufacturing or fabricating an integratedcomputational element for use in an optical computing device.

Optical computing devices, also commonly referred to as“opticoanalytical devices,” can be used to analyze and monitor a samplesubstance in real time. Such optical computing devices will often employa light source that emits electromagnetic radiation that reflects fromor is transmitted through the sample and optically interacts with anoptical processing element to determine quantitative and/or qualitativevalues of one or more physical or chemical properties of the substancebeing analyzed. The optical processing element may be, for example, anintegrated computational element (ICE). One type of an ICE is an opticalthin film interference device, also known as a multivariate opticalelement (MOE). Each ICE can be designed to operate over a continuum ofwavelengths in the electromagnetic spectrum from the UV to mid-infrared(MIR) ranges, or any sub-set of that region. Electromagnetic radiationthat optically interacts with the sample substance is changed andprocessed by the ICE so as to be measured by a detector. The output ofthe detector can be correlated to a physical or chemical property of thesubstance being analyzed.

An ICE (hereafter “ICE core”) typically includes a plurality of opticalthin film layers consisting of various materials whose index ofrefraction and size (e.g., thickness) may vary between each layer. AnICE core design refers to the substrate, the number and thickness of therespective layers, and the refractive indices of each layer of the ICEcore. The layers may be strategically deposited and sized so as toselectively pass predetermined fractions of electromagnetic radiation atdifferent wavelengths configured to substantially mimic a regressionvector corresponding to a particular physical or chemical property ofinterest of a substance of interest. Accordingly, an ICE core designwill exhibit a transmission function that is weighted with respect towavelength. As a result, the output light intensity from the ICE coreconveyed to the detector may be related to the physical or chemicalproperty of interest for the substance.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent disclosure, and should not be viewed as exclusive embodiments.The subject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, withoutdeparting from the scope of this disclosure.

FIG. 1 illustrates an exemplary integrated computational element,according to one or more embodiments.

FIG. 2 depicts a schematic flowchart of an exemplary method ofmanufacturing an optical processing element, according to one or moreembodiments.

FIG. 3 illustrates a cross-sectional side view of an exemplarymultilayer film stack device generated using atomic layer deposition,according to one or more embodiments.

FIG. 4A depicts a top view of the multilayer film stack device of FIG.3, according to one or more embodiments.

FIG. 4B depicts a cross-sectional side view of an optical thin film unitexcised or otherwise cut from the multilayer film stack device of FIG.3, according to one or more embodiments.

FIG. 5 depicts a schematic flowchart of another exemplary method ofmanufacturing an optical processing element, according to one or moreembodiments.

FIG. 6 illustrates an exemplary optical computing device for monitoringa sample substance, according to one or more embodiments.

FIG. 7 illustrates an exemplary wellbore drilling assembly that mayemploy one or more optical computing devices for monitoring a downholesubstance, according to one or more embodiments.

DETAILED DESCRIPTION

The present disclosure is related to optical processing elements and, inparticular, methods of manufacturing or fabricating an integratedcomputational element for use in an optical computing device.

The present disclosure describes improved methods of manufacturingoptical processing elements, such as integrated computational elements(“ICE cores”). In some embodiments, the several thin film layers thatcombine to make up an ICE core are deposited on opposing sides of asubstrate during an atomic layer deposition (ALD) process. The resultingmultilayer film stack device exhibits mirrored thin film layers on eachplanar side of the underlying substrate. The substrate may then becleaved in two by making a planar cut or separation, and therebyrendering mirror ICE cores supported on at least a portion of theremaining substrate. The substrate may then be chemically ormechanically removed from the thin film layers, and the thin film layerscan be subsequently draped over surfaces that would not have survivedthe thin film manufacturing process, or otherwise might have beeninconvenient to coat using ALD techniques. Accordingly, the disclosedembodiments may prove advantageous in doubling the productivity offabricating ICE cores during an ALD process and using the resulting ICEcores as a type of decal that can be selectively arranged on a targetsurface.

The present disclosure also describes building the several thin filmlayers of an ICE core on one side of a substrate supported on itsopposing side on a support structure within a thin film depositionchamber. After suitably fabricating the ICE core, the substrate may thenbe chemically or mechanically removed from the thin film layers, and thethin film layers can be subsequently attached as a type of decal to atarget surface that would not have survived the thin film manufacturingprocess.

The methods disclosed herein may be suitable for fabricating opticalprocessing elements (e.g., ICE cores) for use in the oil and gasindustry, such as for monitoring and detecting oil/gas-relatedsubstances (e.g., hydrocarbons, drilling fluids, completion fluids,treatment fluids, etc.). It will be appreciated, however, that themethods described herein are equally applicable to fabricating ICE coresfor use in other technology fields including, but not limited to, thefood industry, the paint industry, the mining industry, the agriculturalindustry, the medical and pharmaceutical industries, the automotiveindustry, the cosmetics industry, water treatment facilities, and anyother field where it may be desired to monitor substances in real time.

As used herein, the term “characteristic” or “characteristic ofinterest” refers to a chemical, mechanical, or physical property of asubstance or a sample of the substance. The characteristic of asubstance may include a quantitative or qualitative value of one or morechemical constituents or compounds present therein or any physicalproperty associated therewith. Such chemical constituents and compoundsmay be referred to herein as “analytes.”Illustrative characteristics ofa substance that can be analyzed with the help of the optical processingelements described herein can include, for example, chemical composition(e.g., identity and concentration in total or of individual components),phase presence (e.g., gas, oil, water, etc.), impurity content, pH,alkalinity, viscosity, density, ionic strength, total dissolved solids,salt content (e.g., salinity), porosity, opacity, bacteria content,total hardness, transmittance, state of matter (solid, liquid, gas,emulsion, mixtures thereof, etc.), and the like.

As used herein, the term “substance,” or variations thereof, refers toat least a portion of matter or material of interest to be tested orotherwise evaluated with the help of the optical processing elementsdescribed herein. The substance may be any fluid capable of flowing,including particulate solids, liquids, gases (e.g., air, nitrogen,carbon dioxide, argon, helium, methane, ethane, butane, and otherhydrocarbon gases, hydrogen sulfide, and combinations thereof),slurries, emulsions, powders, muds, glasses, mixtures, combinationsthereof, and may include, but is not limited to, aqueous fluids (e.g.,water, brines, etc.), non-aqueous fluids (e.g., organic compounds,hydrocarbons, oil, a refined component of oil, petrochemical products,and the like), acids, surfactants, biocides, bleaches, corrosioninhibitors, foamers and foaming agents, breakers, scavengers,stabilizers, clarifiers, detergents, treatment fluids, fracturingfluids, formation fluids, or any oilfield fluid, chemical, or substancecommonly found in the oil and gas industry. The substance may also referto solid materials such as, but not limited to, rock formations,concrete, solid wellbore surfaces, pipes or flow lines, and solidsurfaces of any wellbore tool or projectile (e.g., balls, darts, plugs,etc.).

As used herein, the term “electromagnetic radiation” refers to radiowaves, microwave radiation, terahertz, infrared and near-infraredradiation, visible light, ultraviolet light, X-ray radiation and gammaray radiation.

As used herein, the term “optically interact” or variations thereofrefers to the reflection, transmission, scattering, diffraction, orabsorption of electromagnetic radiation either on, through, or from anoptical processing element (e.g., an integrated computational element)or a substance being analyzed with the help of the optical processingelement. Accordingly, optically interacted light refers toelectromagnetic radiation that has been reflected, transmitted,scattered, diffracted, or absorbed by, emitted, or re-radiated, forexample, using an optical processing element, but may also apply tooptical interaction with a substance.

As used herein, the term “optical computing device” refers to an opticaldevice that is configured to receive an input of electromagneticradiation associated with a substance and produce an output ofelectromagnetic radiation from an optical processing element arrangedwithin or otherwise associated with the optical computing device. Theoptical processing element may be, for example, an integratedcomputational element (ICE). The electromagnetic radiation thatoptically interacts with the optical processing element is changed so asto be readable by a detector, such that an output of the detector can becorrelated to a particular characteristic of the substance beinganalyzed. The output of electromagnetic radiation from the opticalprocessing element can be reflected, transmitted, and/or dispersedelectromagnetic radiation. Whether the detector analyzes reflected,transmitted, or dispersed electromagnetic radiation may be dictated bythe structural parameters of the optical computing device as well asother considerations known to those skilled in the art. In addition,emission and/or scattering of the fluid, for example via fluorescence,luminescence, Raman, Mie, and/or Raleigh scattering, can also bemonitored by optical computing devices.

As indicated above, the present disclosure provides improved methods ofmanufacturing or fabricating optical processing elements, such asintegrated computational elements (ICE cores), for use in opticalcomputing devices. In operation, an ICE core is capable ofdistinguishing electromagnetic radiation related to a characteristic ofinterest of a substance from electromagnetic radiation related to othercomponents of the substance.

Referring to FIG. 1, illustrated is an exemplary ICE core 100 that maybe fabricated using the presently disclosed methods, according to one ormore embodiments. As illustrated, the ICE core 100 may include aplurality of alternating thin film layers 102 and 104, such as silicon(Si) and SiO₂ (quartz), respectively. In general, these layers 102, 104consist of materials whose index of refraction is high and low,respectively. Other examples of materials might include niobia andniobium, germanium and germania, MgF, SiO, TiO₂, Al₂O₃, and other highand low index materials known in the art. The layers 102, 104 may bestrategically deposited on a substrate 106. In some embodiments, thesubstrate 106 is BK-7 optical glass. In other embodiments, the substrate106 may be another type of optical substrate, such as another opticalglass, silica, sapphire, silicon, germanium, zinc selenide, zincsulfide, or various plastics such as polycarbonate,polymethylmethacrylate (PMMA), polyvinylchloride (PVC), diamond,ceramics, combinations thereof, and the like.

As will be described below, however, the substrate 106 may alternativelybe made of a material that is cleavable in a single plane, and otherwiseeasily removed from the layers 102, 104 by physical or chemical means.For instance, the substrate 106 may be made of mica, pyrolitic carbon,graphite, or graphene.

At the opposite end (e.g., opposite the substrate 106 in FIG. 1), theICE core 100 may include a layer 108 that is generally exposed to theenvironment of the device or installation, and may be able to detect asample substance. The number of layers 102, 104 and the thickness ofeach layer 102, 104 are determined from the spectral attributes acquiredfrom a spectroscopic analysis of a characteristic of the substance beinganalyzed using a conventional spectroscopic instrument. The spectrum ofinterest of a given characteristic typically includes any number ofdifferent wavelengths.

It should be understood that the ICE core 100 depicted in FIG. 1 doesnot in fact represent any particular ICE core configured to detect aspecific characteristic of a given substance, but is provided forpurposes of illustration only. Consequently, the number of layers 102,104 and their relative thicknesses, as shown in FIG. 1, bear nocorrelation to any particular substance or characteristic thereof. Norare the layers 102, 104 and their relative thicknesses necessarily drawnto scale, and therefore should not be considered limiting of the presentdisclosure.

In some embodiments, the material of each layer 102, 104 can be doped ortwo or more materials can be combined in a manner to achieve the desiredoptical characteristic. In addition to solids, the exemplary ICE core100 may also contain liquids and/or gases, optionally in combinationwith solids, in order to produce a desired optical characteristic. Inthe case of gases and liquids, the ICE core 100 can contain acorresponding vessel (not shown), which houses the gases or liquids.Exemplary variations of the ICE core 100 may also include holographicoptical elements, gratings, piezoelectric, light pipe, and/oracousto-optic elements, for example, that can create transmission,reflection, and/or absorptive properties of interest.

The multiple layers 102, 104 may exhibit different refractive indices.By properly selecting the materials of the layers 102, 104 and theirrelative thickness and spacing, the ICE core 100 may be configured toselectively transmit or reflect predetermined fractions ofelectromagnetic radiation at different wavelengths. Each wavelength isgiven a predetermined weighting or loading factor. The thickness andspacing of the layers 102, 104 may be determined using a variety ofapproximation methods from the spectrum of the characteristic or analyteof interest. These methods may include inverse Fourier transform (IFT)of the optical transmission spectrum and structuring the ICE core 100 asthe physical representation of the IFT. The approximations convert theIFT into a structure based on known materials with constant refractiveindices.

The weightings that the layers 102, 104 of the ICE core 100 apply ateach wavelength are set to the regression weightings described withrespect to a known equation, or data, or spectral signature. Forinstance, when electromagnetic radiation interacts with a substance,unique physical and chemical information about the substance is encodedin the electromagnetic radiation that is reflected from, transmittedthrough, or radiated from the substance. This information is oftenreferred to as the spectral “fingerprint” of the substance. The ICE core100 may be configured to perform the dot product of the receivedelectromagnetic radiation and the wavelength dependent transmissionfunction of the ICE core 100. The wavelength dependent transmissionfunction of the ICE core 100 is dependent on the material refractiveindex of each layer, the number of layers 102, 104 and thickness of eachlayer 102, 104. As a result, the output light intensity of the ICE core100 is related to the characteristic or analyte of interest.

As further explanation, accurately determining the regression vector ofthe characteristic of interest in the sample substance provides a meansfor an optical computing device to determine or otherwise calculate aconcentration of said characteristic in the sample substance. Theregression vector for each characteristic may be determined usingstandard procedures that will be familiar to one having ordinary skillin the art. For example, analyzing the spectrum of the sample substancemay include determining a dot product of the regression vector for eachcharacteristic of the sample substance being analyzed. As one ofordinary skill in art will recognize, a dot product of a vector is ascalar quantity (i.e., a real number). While the dot product value isbelieved to have no physical meaning by itself (e.g., it may return apositive or negative result of any magnitude), comparison of the dotproduct value of a sample substance with dot product values obtained forknown reference standards and plotted in a calibration curve may allowthe sample substance dot product value to be correlated with aconcentration or value of a characteristic, thereby allowing unknownsample substances to be accurately analyzed.

To determine the dot product, one simply multiples the regressioncoefficient of the regression vector at a given wavelength by thespectral intensity at the same wavelength. This process is repeated forall wavelengths analyzed, and the products are summed over the entirewavelength range to yield the dot product. Those skilled in the art willrecognize that two or more characteristics may be determined from asingle spectrum of the sample substance by applying a correspondingregression vector for each characteristic.

In practice, it is possible to derive information from electromagneticradiation interacting with a sample substance by, for example,separating the electromagnetic radiation from several samples intowavelength bands and performing a multiple linear regression of the bandintensity against a characteristic of interest determined by anothermeasurement technique for each sample substance. The measuredcharacteristic may be expressed and modeled by multiple linearregression techniques that will be familiar to one having ordinary skillin the art. Specifically, if y is the measured value of theconcentration or characteristic, y may be expressed as in Equation 1:y=a ₀ +a ₁ w ₁ +a ₂ w ₂ +a ₃ w ₃ +a ₄ w ₄+ . . .  Equation (1)

where each ‘a’ is a constant determined by the regression analysis andeach ‘w’ is the light intensity for each wavelength band. Depending onthe circumstances, the estimate obtained from Equation (1) may beinaccurate, for example, due to the presence of other characteristicswithin the sample substance that may affect the intensity of thewavelength bands. A more accurate estimate may be obtained by expressingthe electromagnetic radiation in terms of its principal components.

To obtain the principal components, spectroscopic data is collected fora variety of similar sample substances using the same type ofelectromagnetic radiation. For example, following exposure to eachsample substance, the electromagnetic radiation may be collected and thespectral intensity at each wavelength may be measured for each samplesubstance. This data may then be pooled and subjected to alinear-algebraic process known as singular value decomposition (SVD) inorder to determine the principal components. Use of SVD in principalcomponent analysis will be well understood by one having ordinary skillin the art. Briefly, however, principal component analysis is adimension reduction technique that takes ‘m’ spectra with ‘n’independent variables and constructs a new set of eigenvectors that arelinear combinations of the original variables. The eigenvectors may beconsidered a new set of plotting axes. The primary axis, termed thefirst principal component, is the vector that describes most of the datavariability. Subsequent principal components describe successively lesssample variability, until the higher order principal componentsessentially describe only spectral noise.

Typically, the principal components are determined as normalizedvectors. Thus, each component of an electromagnetic radiation sample maybe expressed as x_(n)z_(n), where x_(n) is a scalar multiplier and z_(n)is the normalized component vector for the n^(th) component. That is,z_(n) is a vector in a multi-dimensional space where each wavelength isa dimension. Normalization determines values for a component at eachwavelength so that the component maintains its shape and the length ofthe principal component vector is equal to one. Thus, each normalizedcomponent vector has a shape and a magnitude so that the components maybe used as the basic building blocks of any electromagnetic radiationsample having those principal components. Accordingly, eachelectromagnetic radiation sample may be described by a combination ofthe normalized principal components multiplied by the appropriate scalarmultipliers, as set forth in Equation (2):x ₁ z ₁ +x ₂ z ₂ + . . . +x _(n) z _(n)  Equation (2)

The scalar multipliers x_(n) may be considered the “magnitudes” of theprincipal components in a given electromagnetic radiation sample whenthe principal components are understood to have a standardized magnitudeas provided by normalization.

Because the principal components are orthogonal, they may be used in arelatively straightforward mathematical procedure to decompose anelectromagnetic radiation sample into the component magnitudes, whichmay accurately describe the data in the original electromagneticradiation sample. Since the original electromagnetic radiation samplemay also be considered a vector in the multi-dimensional wavelengthspace, the dot product of the original signal vector with a principalcomponent vector is the magnitude of the original signal in thedirection of the normalized component vector. That is, it is themagnitude of the normalized principal component present in the originalsignal. This is analogous to breaking a vector in a three dimensionalCartesian space into its X, Y and Z components. The dot product of thethree-dimensional vector with each axis vector, assuming each axisvector has a magnitude of 1, gives the magnitude of the threedimensional vector in each of the three directions. The dot product ofthe original signal and some other vector that is not perpendicular tothe other three dimensions provides redundant data, since this magnitudeis already contributed by two or more of the orthogonal axes.

Because the principal components are orthogonal to each other, the dotproduct of any principal component with any other principal component iszero. Physically, this means that the components do not interfere witheach other. If data is altered to change the magnitude of one componentin the original electromagnetic radiation signal, the other componentsremain unchanged. In the analogous Cartesian example, reduction of the Xcomponent of the three dimensional vector does not affect the magnitudesof the Y and Z components.

Principal component analysis provides the fewest orthogonal componentsthat can accurately describe the data carried by the electromagneticradiation samples. Thus, in a mathematical sense, the principalcomponents are components of the original electromagnetic radiation thatdo not interfere with each other and that represent the most compactdescription of the spectral signal. Physically, each principal componentis an electromagnetic radiation signal that forms a part of the originalelectromagnetic radiation signal. Each principal component has a shapeover some wavelength range within the original wavelength range. Summingthe principal components may produce the original signal, provided eachcomponent has the proper magnitude, whether positive or negative.

The principal components may comprise a compression of the informationcarried by the total light signal. In a physical sense, the shape andwavelength range of the principal components describe what informationis in the total electromagnetic radiation signal, and the magnitude ofeach component describes how much of that information is present. Ifseveral electromagnetic radiation samples contain the same types ofinformation, but in differing amounts, then a single set of principalcomponents may be used to describe (except for noise) eachelectromagnetic radiation sample by applying appropriate magnitudes tothe components. The principal components may be used to provide anestimate of the characteristic of the sample substance based upon theinformation carried by the electromagnetic radiation that has interactedwith that sample substance. Differences observed in spectra of samplesubstances having varying quantities of an analyte or values of acharacteristic may be described as differences in the magnitudes of theprincipal components. Thus, the concentration of the characteristic maybe expressed by the principal components according to Equation (3) inthe case where four principal components are used:y=a ₀ +a ₁ x ₁ +a ₂ x ₂ +a ₃ x ₃ +a ₄ x ₄  Equation (3)

where ‘y’ is a concentration or value of a characteristic, each a is aconstant determined by the regression analysis, and x₁, x₂, x₃ and x₄are the first, second, third, and fourth principal component magnitudes,respectively. Equation (3) may be referred to as a regression vector.The regression vector may be used to provide an estimate for theconcentration or value of the characteristic for an unknown sample.

Regression vector calculations may be performed by computer, based onspectrograph measurements of electromagnetic radiation by wavelength.The spectrograph system spreads the electromagnetic radiation into itsspectrum and measures the spectral intensity at each wavelength over thewavelength range. Using Equation (3), the computer may read theintensity data and decompose the electromagnetic radiation sample intothe principal component magnitudes x_(n) by determining the dot productof the total signal with each component. The component magnitudes arethen applied to the regression equation to determine a concentration orvalue of the characteristic.

To simplify the foregoing procedure, however, the regression vector maybe converted to a form that is a function of wavelength so that only onedot product is determined. Each normalized principal component vectorz_(n) has a value over all or part of the total wavelength range. Ifeach wavelength value of each component vector is multiplied by theregression constant and corresponding to the component vector, and ifthe resulting weighted principal components are summed by wavelength,the regression vector takes the form of Equation (4):y=a ₀ +b ₁ u ₁ +b ₂ u ₂ + . . . +b _(n) u _(n)  Equation (4)

where a₀ is the first regression constant from Equation (3), b_(n) isthe sum of the multiple of each regression constant a_(n) from Equation(3) and the value of its respective normalized regression vector atwavelength ‘n’, and u_(n) is the intensity of the electromagneticradiation at wavelength ‘n’. Thus, the new constants define a vector inwavelength space that directly describes a concentration orcharacteristic of a sample substance. The regression vector in the formof Equation (4) represents the dot product of an electromagneticradiation sample with this vector.

Normalization of the principal components provides the components withan arbitrary value for use during the regression analysis. Accordingly,it is very unlikely that the dot product value produced by theregression vector will be equal to the actual concentration orcharacteristic value of a sample substance being analyzed. The dotproduct result is, however, proportional to the concentration orcharacteristic value. As discussed above, the proportionality factor maybe determined by measuring one or more known calibration samples byconventional means and comparing the result to the dot product value ofthe regression vector. Thereafter, the dot product result can becompared to the value obtained from the calibration standards in orderto determine the concentration or characteristic of an unknown samplebeing analyzed.

Referring now to FIG. 2, with continued reference to FIG. 1, illustratedis a schematic flowchart of an exemplary method 200 of manufacturing anoptical processing element, according to one or more embodiments.Optical processing elements that result from following the method 200may be substantially similar to the ICE core 100 of FIG. 1, andotherwise useful in analyzing a sample substance for an analyte orcharacteristic of interest associated with the sample substance.

According to the method 200, a substrate for the optical processingelement may first be provided, as at 202. A suitable substrate may besimilar to the substrate 106 described above with reference to FIG. 1.Preferably, the substrate exhibits optical properties that are compliantwith the optical bandwidth of interest (i.e., significantly flat andhigh % transmission profile). Suitable substrate materials also includethose that exhibit a physical stability sufficient to withstand elevatedtemperatures and extreme conditions typically associated with thin filmdeposition processes and techniques.

In at least one embodiment, the substrate may be generally disc-shapedand therefore include a first surface and a second surface that isopposite or substantially opposite the first surface. In embodimentswhere the first and second surfaces are substantially opposite oneanother, the first and second surfaces may be planar surfaces that areparallel to one another or slightly offset from parallel, withoutdeparting from the scope of the disclosure.

In some embodiments, the substrate may be made of a material that iscleavable in a single plane, such that it may be subsequently cleaved inplane or otherwise removed from the optical processing element usingmechanical means. In other embodiments, the substrate may be made of amaterial that may be removed from the optical processing element usingchemical means. In yet other embodiments, the substrate may be made of amaterial that can be removed from the optical processing element usingboth mechanical and chemical means. Suitable materials for the substrateinclude, but are not limited to, mica, pyrolitic carbon, graphite,graphene, and any other materials that exhibit substantially similarchemical compositions or atomic structures. In at least one embodiment,the substrate may be a salt (i.e., NaCl) that is polished and thensubsequently flash-coated with aluminum to get the desire reactivesurface for a substrate. In yet other embodiments, the substrate may bea plastic, such as polyethylene terephthalate (PET), or one or morecellulose films.

In some embodiments, the method 200 may include preparing the surface ofthe substrate, as at 204. Preparing the surface of the substrate mayinclude reducing the thickness of the substrate until a desired orpredetermined thickness of the substrate is achieved. In someembodiments, the thickness of the substrate may be reduced throughchemical means, such as etching or oxidation. In other embodiment,however, especially in embodiments where the substrate is graphite, thethickness of the substrate may be sequentially reduced by cleaving thesurface of the substrate and thereby producing individual layers orsheets of graphene. In at least one embodiment, the graphene sheets maybe used as a suitable substrate, for example. Accordingly, the substratemay exhibit a very small thickness, such as in the range of a fewangstroms.

In other embodiments, preparing the surface of the substrate may includechemically treating the surface of the substrate so that it becomes moreamenable or receptive to a particular thin film deposition process. Forinstance, in the case where atomic layer deposition (ALD) is used, theALD process can be surface selective. In other words, some of thematerials used to build the layers (i.e., layers 102, 104 of FIG. 1) ofthe optical processing element may not chemically bond or otherwiseadhere to the given substrate. To accommodate layer chemistries that maynot directly adhere to the given substrate, the surface of the substratemay be coated or otherwise pre-treated with a reactive agent, such asaluminum, titanium, silicon, germanium, indium, gallium, and arsenic.This may be done using sputtering techniques known to those skilled inthe art. The reactive agent may then be reacted in order to generate anoxide surface that may be more responsive to ALD techniques. In otherembodiments, the surface of the substrate may be treated with anoxidation product, without departing from the scope of the disclosure.

Once the surface of the substrate is properly or suitably prepared,multiple optical thin films may be deposited on the substrate via a thinfilm deposition process to generate a multilayer film stack device, asat 206. In the present embodiment, the thin film deposition process maybe an ALD process, such as those generally known to those skilled in theart. In embodiments discussed below, however, the thin film depositionprocess may be any chemical or physical thin film deposition techniqueknown to those skilled in the art including, but not limited to,plating, chemical solution deposition, spin coating, chemical vapordeposition, plasma enhanced chemical vapor deposition, physical vapordeposition, sputtering, pulsed laser deposition, cathodic arcdeposition, electrohydrodynamic deposition (i.e., electrospraydeposition), and ion-assisted e-beam deposition.

In the present embodiment, subjecting the substrate to an ALD process,as at 206, may include introducing the substrate into an ALD reactionchamber. The substrate may be hung or suspended within the ALD reactionchamber such that both planar sides of the substrate may be evenlycoated during each stage of the deposition process. In at least oneembodiment, in order to properly suspend the substrate within the ALDreaction chamber, the substrate may be secured to a clip or othersupport structure associated with the ALD reaction chamber.

Once the substrate is suitably arranged (i.e., hung) within the ALDreaction chamber, the ALD process may then proceed to sequentially(i.e., consecutively) grow the various layers (i.e., layers 102, 104 ofFIG. 1) on the substrate. Briefly, this process includes introducing afirst gaseous compound or “precursor” into the ALD reaction chamber tochemically bond to the substrate; purging or evacuating the ALD reactionchamber to remove any non-reacted precursors and/or gaseous reactionby-products; introducing a second precursor into the ALD reactionchamber to chemically react to the substrate bonded precursor of theprevious cycle to form a monolayer; purging or evacuating the ALDreaction chamber to remove any non-reacted precursors and/or gaseousreaction by-products of the second precursor; and repeating theforegoing steps as many times as required for the desired number oflayers and the desired thickness of each layer.

Due to self-terminating reactions inherent in ALD processing, ALD ischaracterized as a surface-controlled process, where the predominantprocess parameters of control include the precursors (and their flowrates), the substrate, and the ambient temperature inside the ALDreaction chamber. Moreover, because of the surface control that isinherent in ALD processes, the resulting layers deposited on thesubstrate are extremely conformal and otherwise uniform in thickness oneach side of the substrate.

Referring briefly to FIG. 3, with continued reference to FIG. 2,illustrated is a cross-sectional side view of an exemplary multilayerfilm stack device 300 that may be generated using the foregoing ALDprocess, according to one or more embodiments. As depicted in FIG. 3,the substrate 106 is encased and otherwise entirely covered with aplurality of alternating thin film layers 102 and 104, similar to thosedescribed above with reference to FIG. 1. It is noted that the number oflayers 102, 104 and their relative thicknesses, as depicted in FIG. 3,are not drawn to scale, and therefore should not be considered limitingof the present disclosure.

Notably, the layers 102, 104 are depicted as being deposited uniformlyon all sides of the substrate 106. More particularly, the substrate 106has first and second surfaces 302 a and 302 b, respectively, and thelayers 102, 104 are built up or “grown” uniformly on each surface 302a,b. Accordingly, the multilayer film stack device 300 exhibits layers102, 104 that are mirrored on each surface 302 a,b.

In at least one embodiment, the initial or first layer 102 deposited onthe substrate may be made of a metal oxide material, such as aluminumoxide (Al₂O₃) or titanium dioxide (TiO₂). As will be appreciated, theoxide material of the first layer 102 may prove advantageous in creatinga good adhesion to the substrate 106, and thereby protecting the thinfilms from inadvertent removal from the substrate 106. In someembodiments, one or both of the first and last layers 102, 104 of themultilayer film stack device 300 may be deposited to a thickness that isgreater than the other interposing layers 102, 104. As will beappreciated, providing thicker first and/or last layers 102, 104 mayprovide greater core mechanical strength to the multilayer film stackdevice 300, thereby resulting in a more robust multilayer film stackdevice 300.

Referring again to FIG. 2, the method 200 may also include cleaving thesubstrate to produce at least two mirror optical thin film stacks, as at208. Those skilled in the art will readily recognize that there aremultiple ways to cleave the substrate. In one embodiment, for example,the optical thin film stack can be cleaved in two by making a planar cutthrough the substrate. This can be done with a laser or a focused ionbeam, for example. In other embodiments, the substrate may bemechanically separated, such as through the application of a shear loadacross the substrate that results in the substrate shearing along anatomic layer associated therewith. Advantageously, since the substrateis made from a cleavable material that is shearable along acrystallographic axis, cleaving the substrate mechanically may notcompromise the integrity of the mirror optical thin film stacks.

In yet other embodiments, one or more additional layers may be depositedon the substrate that exhibit different thermal expansion coefficientsthan the other thin film layers in the plane of deposition. Upon themultilayer film stack device assuming a large temperature change, thesubstrate may separate along the layers of dissimilar thermal expansioncoefficients. In some embodiments, for example, this may be accomplishedby depositing layers of aluminum inter-digeted (e.g., alternating) withone or more layers of iron oxides. Such alternating layers may proveadvantageous in generating a thermal reaction that causes the substrateto separate.

In some embodiments, prior to or after cleaving the substrate, themethod 200 may include subdividing the multilayer film stackdevice/stacks into multiple smaller optical thin film units, as at 210.Accordingly, in some embodiments, the multilayer film stack device 300of FIG. 3 may be subdivided into multiple smaller optical thin filmunits prior to cleaving the underlying substrate 106. In otherembodiments, however, after cleaving the substrate 106 of the multilayerfilm stack device 300 to produce the mirror optical thin film stacks, asat 208 above, each resulting optical thin film stack may be subdividedinto multiple smaller optical thin film units.

Referring to FIGS. 4A and 4B, with continued reference to FIG. 3,illustrated are views of the multilayer film stack device 300, accordingto one or more embodiments. More particularly, FIG. 4A depicts a topview of the multilayer film stack device 300, and FIG. 4B depicts across-sectional side view of an optical thin film unit excised orotherwise cut from the multilayer film stack device 300.

As illustrated In FIG. 4A, the substrate 106 used to support the severaloptical thin film layers 102, 104 is generally circular, therebyresulting in a generally circular multilayer film stack device 300. Themultilayer film stack device 300 is depicted as having been subdivided(e.g., diced, partitioned, apportioned, etc.) into four optical thinfilm units 402 (shown as optical thin film units 402 a, 402 b, 402 c,and 402 d. Subdividing the multilayer film stack device 300 intomultiple optical thin film units 402 a-d may be accomplished by variousthin film dicing techniques known to those skilled in the art, such aslaser dicing.

Each optical thin film unit 402 a-d includes a portion of the substrate106 and, similar to the multilayer film stack device 300 depicted inFIG. 3, each optical thin film unit 402 a-d includes mirrored stacks oflayers 102, 104 built up or grown uniformly on each surface 302 a,b ofthe substrate 106. FIG. 4B depicts a cross-sectional side view of thefirst optical thin film unit 402 a, but it will be appreciated that theother optical thin film units 402 b-d would be substantially similar instructure. It will also be appreciated that, while only four opticalthin film units 402 a-d are depicted in FIG. 4A, the multilayer filmstack device 300 may be diced into more or less than four optical thinfilm units 402 a-d, without departing from the scope of the disclosure.The number of optical thin film units will depend primarily on the sizeof the substrate 106 and the desired size of the resulting opticalprocessing elements.

Referring again to FIG. 2, once the optical thin film units aresuccessfully diced or otherwise subdivided from the multilayer filmstack device, the substrate from each optical thin film unit may then becleaved, as at 208, and as generally described above. Cleaving theoptical thin film units at the substrate will result in correspondingoptical thin film stacks having a portion of the substrate remainingthereon.

The method 200 may then include removing the remaining portions of thesubstrate from the optical thin film stacks, as at 212, therebyresulting in corresponding stacks of optical thin films that can be usedas ICE cores, as generally described above. It should be noted that“removing” the substrate from the optical thin film stack also includesminimizing the thickness of the substrate and otherwise not entirelyremoving every remnant of the substrate from the optical thin films.Accordingly, the terms “removing” and “minimizing” are usedinterchangeably herein, but will generally be discussed in terms of“removing” the substrate.

The substrate can be removed from the optical thin film stacks eitherchemically or mechanically. In removing the substrate chemically, layersof the substrate may be removed by subjecting the substrate to lowtemperature oxidation. In other embodiments, layers of the substrate maybe removed by subjecting the substrate to elevated temperatureoxidation, such as exposing the substrate to oxygen (O₂) or ozone (O₃)and thereby combusting the substrate. In yet other embodiments, thesubstrate may be removed by placing the optical thin film stack in asolvent bath and allowing a solvent to react with and otherwise etch ordissolve the substrate. Contamination may be controlled by processingthe substrates at reduced pressures.

In removing the substrate mechanically, layers of the substrate may beremoved sequentially using shear forces applied tangentially against thesubstrate. In other embodiments, especially in the case of graphite,conventional adhesive tape may be used to sequentially or systematicallyremove atomic layers of graphite (i.e., graphene layers) until a desiredthickness of the substrate remains or the substrate is removedaltogether from the first layer. In yet other embodiments, the opticalthin films may be pliable or bendable such that when the optical thinfilm stack is bent slightly with a mechanical force applied on opposingsides of the stack, the substrate is able to “pop off” the first layeror is otherwise forcibly removed from the optical thin film stack. Suchmay be the case when the substrate material is mica, for example.

It should be noted that the substrate could be removed prior to (or inplace of) cleaving the substrate. Accordingly, in at least oneembodiment, steps 210 and 212 of the method 200 may be reversed, withoutdeparting from the scope of the disclosure. In such cases, the chemicalor mechanical methods of removing the substrate may also result incleaving the substrate, as at 208, such that the corresponding opticalthin film stacks result.

In some embodiments, the method 200 may further include placing the ICEcores on a target surface, as at 214. More particularly, the ICE coresresulting from cleaving and/or subdividing the multilayer film stackdevice may be attached or otherwise adhered to a secondary opticalelement that either would not have survived the ALD process (or otherthin film deposition processes) or would be impractical to place in theALD reaction chamber. The secondary optical element may be any opticalelement, device, mechanism, or component that may be used in the opticalcomputing devices described herein, and the ICE core may operatetherewith in order to determine analytes of interest of a samplesubstance. For example, the secondary optical element may be, but is notlimited to, a sector of a filter wheel, a band pass filter, a lens, asurface of an optical fiber, a sampling window, a sapphire opticalelement, a non-planar optical element (e.g., the surface of a lamp,light bulb, or other source of electromagnetic radiation), and adetector.

In some embodiments, the ICE cores may be manually placed on thesecondary optical element. This may be accomplished by hand or with thehelp of a tool or device, such as pliers, tweezers, or the like. Inembodiments where the substrate is graphite and at least a portion ofthe graphite substrate remains on a given ICE core, magnetic tweezersmay be used to manipulate the position of the given ICE core. As knownin the art, graphite is a diamagnetic material that generally creates amagnetic field in opposition of an applied magnetic field. Accordingly,magnetic tweezers may be used to capture and levitate the given ICE corebetween the opposing magnets of the tweezers. The given ICE core maythen be brought to a target surface of the secondary optical element andappropriately arranged thereon.

An adhesive may be used to secure the ICE core to the target surface. Inat least one embodiment, the magnetic tweezers (or another magnet) maybe used to apply a magnetic clamping or pinning force on the ICE coreagainst the target surface until the adhesive properly sets. Themagnetic repulsion effected on the graphite portion of the ICE core bythe magnet may serve to maintain the ICE core securely seated on thetarget surface. Suitable adhesives include any optically transparentadhesive, or any adhesive that exhibits little to no spectral features.In some embodiments, however, the adhesive could also be applied aboutthe periphery of the ICE core (as opposed to its central locations) sothat light passing through the ICE core and the secondary opticalelement is not adversely affected by the adhesive. Once the adhesivedries, the magnetic clamping force may be removed from the ICE core and,if desired, the remaining portions of the substrate may be chemicallyetched or otherwise removed from the optical thin film layers.

In other embodiments, the ICE core may be bonded or otherwise attachedto the secondary optical element at the target surface using knownsintering, welding, or bonding techniques. Such bonding techniques mayinclude, but are not limited to low temperature glass frit bonding,glass soldering, seal glass bonding, pressure bonding, and waferbonding. In such embodiments, the edges of the ICE core may be sinteredto the target surface. In embodiments where the target surface is madeof a low temperature melting glass or plastic, the target surface may bepartially melted in order to securely bond the ICE core to the secondaryoptical element.

In yet other embodiments, the remaining portions of the substrate on theICE core may be chemically etched or otherwise reacted in order to forma proper adhesion to the secondary optical element. More specifically, amagnet or other magnetic device (i.e., magnetic tweezers, etc.) may beused to push or otherwise pin the ICE core against the target surfacewhile the substrate is chemically etched or reacted. Upon chemicallyreacting the substrate with oxygen (O₂) or ozone (O₃), for example, theresulting combustion process may serve to partially melt a plastic orglass target surface of the secondary optical element and thereby bondthe ICE core thereto.

Placing the ICE cores on the target surface, as at 214, may also beaccomplished in a solvent bath. More particularly, in embodiments wherethe substrate is removed chemically in a solvent bath, as at 212, theICE cores may be floating in the solvent bath following dissolution oretching of the substrate. In such cases, a secondary optical element maybe manipulated up through or otherwise within the solvent bath tocapture the given ICE core using surface tension forces. The given ICEcore may engage the secondary optical element at the target location anddrape itself over its surface. In other embodiments, the secondaryoptical element may be disposed within the solvent bath and the solventmay be drained to allow the ICE core to land on and drape over thesecondary optical element at the target location. Once the solventdries, the ICE core may form a permanent part of the secondary opticalelement. In some embodiments, however, the ICE core may be sintered,welded, or bonded to the target surface, as generally described above,without departing from the scope of the disclosure.

Referring now to FIG. 5, illustrated is a schematic flowchart of anotherexemplary method 500 of manufacturing an optical processing element,according to one or more embodiments. The method 500 may be similar insome respects to the method 200 of FIG. 2 and therefore may be bestunderstood with reference thereto, where like elements or steps frommethod 200 are not described again in detail below. Similar to themethod 200 of FIG. 2, optical processing elements that result fromfollowing the method 500 may be substantially similar to the ICE core100 of FIG. 1, and otherwise useful in analyzing a sample substance foran analyte or characteristic of interest associated with the samplesubstance.

According to the method 500, a substrate for the optical processingelement may first be provided, as at 502. Again, suitable substrates maybe made of a material that is cleavable in a single plane and/or amaterial that may be removed from the optical processing element usingchemical means. Suitable substrate materials also include those that areable to withstand elevated temperatures that are typically associatedwith thin film deposition processes and techniques. Suitable materialsfor the substrate include, but are not limited to, mica, pyroliticcarbon, graphite, graphene, and any other materials that exhibitsubstantially similar chemical compositions or atomic structures.

In some embodiments, the method 500 may include preparing the surface ofthe substrate, as at 504, and similar to 202 of the method 200. Asdiscussed above, preparing the surface of the substrate may includechemically or mechanically reducing the thickness of the substrate untila desired or predetermined thickness of the substrate is achieved.Preparing the surface of the substrate may also include chemicallytreating the surface of the substrate so that it becomes more amenableor receptive to a particular thin film deposition process.

Once the surface of the substrate is properly or suitably prepared,multiple optical thin films may be deposited on the substrate via a thinfilm deposition process, as at 506, and thereby generating a multilayerfilm stack device. In the present embodiment of method 500, the thinfilm deposition process is not limited to an ALD process, but ratherincludes any chemical or physical thin film deposition technique knownto those skilled in the art including, but not limited to, plating,chemical solution deposition, spin coating, chemical vapor deposition,plasma enhanced chemical vapor deposition, physical vapor deposition,sputtering, pulsed laser deposition, cathodic arc deposition,electrohydrodynamic deposition (i.e., electrospray deposition), andion-assisted e-beam deposition.

Depositing the multiple optical thin films on the substrate may includeintroducing the substrate into a reaction chamber and arranging thesubstrate on a support structure within the reaction chamber such thatone surface of the substrate is exposed to the environment of thereaction chamber. During the deposition process, the exposed surface ofthe substrate will have the optical thin films sequentially (i.e.,consecutively) deposited thereon. As with the embodiments of method 200,any number of optical thin film layers exhibiting any desired thicknessmay be deposited on the substrate. Moreover, in at least one embodiment,the initial or first layer deposited on the substrate may be made of ametal oxide material, such as aluminum oxide (Al₂O₃) or titanium dioxide(TiO₂), in order to create a suitable adhesion to the substrate, andthereby protecting the deposited optical thin films from inadvertentremoval from the substrate. The first and/or final optical thin filmlayers may also be deposited to a thickness generally greater than theinterposing optical thin film layers, and thereby generating a morerobust multilayer film stack device.

After the optical thin film layers are deposited on the substrate andthe multilayer film stack device is produced, as at 506, the method 500may include removing the substrate from the multilayer film stackdevice, as at 508, and thereby providing a stack of optical thin filmsthat can be used as an ICE core, as generally described above. Again, itis noted that “removing” the substrate from the optical thin film stackalso includes minimizing the thickness of the substrate and otherwisenot entirely removing every remnant of the substrate from the opticalthin films. Accordingly, the term “removing” is used herein to denoteminimizing the substrate or removing it altogether from the optical thinfilms.

As with the embodiments of method 200, the substrate can be removed fromthe optical thin film stack either chemically or mechanically. Inremoving the substrate chemically, layers of the substrate may beremoved by subjecting the substrate to low temperature oxidation,exposing the substrate to oxygen (O₂) or ozone (O₃), and/or placing theoptical thin film stack in a solvent bath and allowing a solvent to etchor dissolve the substrate. In removing the substrate mechanically,layers of the substrate may be removed sequentially using shear forcesapplied tangentially against the substrate or, as in the case ofgraphite, conventional adhesive tape may be used to sequentially removeatomic layers of graphite (i.e., graphene layers) until a desiredthickness (including no thickness) of the substrate remains. In yetother embodiments, the optical thin films may be pliable such that whenthe optical thin film stack is bent, the substrate is able to “pop off”the first layer or is otherwise forcibly removed from the optical thinfilm stack. Such may be the case when the substrate material is mica,for example.

The method 500 may further include subdividing the optical thin filmstack into multiple smaller optical thin film stacks, as at 510, wherebyeach smaller optical thin film stack may be used as an ICE core. As willbe appreciated, however, subdividing the optical thin film stack mayequally be performed prior to removing the substrate from the multilayerfilm stack device, as at 508, and thereby generating multiple smalleroptical thin film stacks having a portion of the substrate remainingthereon. Accordingly, in at least one embodiment, steps 508 and 510 ofthe method 500 may be reversed, without departing from the scope of thedisclosure.

The method 500 may further include placing the ICE core(s) on a targetsurface, as at 512. Placing the ICE core(s) on a target surface mayinclude attaching or otherwise adhering the ICE core(s) to a secondaryoptical element that either would not have survived the thin filmdeposition process or would otherwise have been impractical to place inthe thin film reaction chamber. The secondary optical element is definedabove, and therefore will not be described again in detail.

Similar to step 214 of the method 200 of FIG. 2, the ICE core(s) may bemanually placed on the secondary optical element, such as by hand orotherwise through the use of a tool or device. The ICE core(s) may alsobe placed on the target surface while floating in a solvent bath, suchas by capturing a given ICE core using surface tension forces while theICE core floats in the solvent bath, or draining the fluids from thesolvent bath such that the given ICE core lands on and drapes itselfover the secondary optical element at a target surface. Once the solventdries, the ICE core may be attached to the secondary optical element. Inother embodiments, however, the ICE core may be bonded or otherwiseattached to the secondary optical element at the target surface usingknown sintering, welding, or bonding techniques.

In some embodiments, an adhesive may be used to secure the ICE core(s)to the target surface. The adhesive may be optically transparent orotherwise applied about the periphery of the ICE core (as opposed to itscentral locations) so that light passing through the ICE core and thesecondary optical element is not adversely affected by the adhesive.Once the adhesive dries, the ICE core(s) may be effectively bonded tothe secondary optical element. In some embodiments, the remainingportions of the substrate (if any) may then be chemically etched orotherwise removed from the optical thin film layers. In otherembodiments, the ICE core(s) may be bonded or otherwise attached to thesecondary optical element at the target surface using known sintering,welding, or bonding techniques. In yet other embodiments, any remainingportions of the substrate on the ICE core(s) may be chemically etched orotherwise reacted in order to melt portions of the underlying targetsurface or the ICE core and thereby form a proper adhesion to thesecondary optical element.

Referring now to FIG. 6, illustrated is an exemplary optical computingdevice 600 for monitoring a sample substance 602, according to one ormore embodiments. In the illustrated embodiment, the sample substance602 may be contained or otherwise flowing within an exemplary flow path604. The flow path 604 may be a flow line, a pipeline, a wellbore, anannulus defined within a wellbore, or any flow lines or pipelinesextending to/from a wellbore. The sample substance 602 present withinthe flow path 604 may be flowing in the general direction indicated bythe arrows A (i.e., from upstream to downstream). As will beappreciated, however, the flow path 604 may be any other type of flowpath, such as a mud pit (i.e., used for drilling fluids and the like) orany other containment or storage vessel, and the sample substance 602may not necessarily be flowing in the direction A while the samplesubstance 602 is being monitored. As such, portions of the flow path 604may be arranged substantially vertical, substantially horizontal, or anydirectional configuration therebetween, without departing from the scopeof the disclosure.

The optical computing device 600 may be configured to determine acharacteristic of interest in the sample substance 602 or a componentpresent within the sample substance 602. In some embodiments, the device600 may include an electromagnetic radiation source 608 configured toemit or otherwise generate electromagnetic radiation 610. Theelectromagnetic radiation source 608 may be any device capable ofemitting or generating electromagnetic radiation, such as, but notlimited to, a light bulb, a light emitting diode (LED), a laser, ablackbody, a photonic crystal, an X-Ray source, combinations thereof, orthe like. In some embodiments, a lens 612 may be configured to collector otherwise receive the electromagnetic radiation 610 and direct a beam614 of electromagnetic radiation 610 toward the sample substance 602. Inother embodiments, the lens 612 may be omitted from the device 600 andthe electromagnetic radiation 610 may instead be directed toward thesample substance 602 directly from the electromagnetic radiation source608.

In one or more embodiments, the device 600 may also include a samplingwindow 616 arranged adjacent to or otherwise in contact with the samplesubstance 602 for detection purposes. The sampling window 616 may bemade from a variety of transparent, rigid or semi-rigid materials thatare configured to allow transmission of the electromagnetic radiation610 therethrough. After passing through the sampling window 616, theelectromagnetic radiation 610 impinges upon and optically interacts withthe sample substance 602, including any components present within thesample substance 602. As a result, optically interacted radiation 618 isgenerated by and reflected from the sample substance 602. Those skilledin the art, however, will readily recognize that alternative variationsof the device 600 may allow the optically interacted radiation 618 to begenerated by being transmitted, scattered, diffracted, absorbed,emitted, or re-radiated by and/or from the sample substance 602, withoutdeparting from the scope of the disclosure.

The optically interacted radiation 618 generated by the interaction withthe sample substance 602 may be directed to or otherwise be received byan ICE core 620 arranged within the device 600. The ICE core 620 may bea spectral component substantially similar to the ICE core 100 describedabove with reference to FIG. 1 and fabricated using one of the methods200, 500 of FIGS. 2 and 5, respectively, as discussed above.Accordingly, in operation the ICE core 620 may be configured to receivethe optically interacted radiation 618 and produce modifiedelectromagnetic radiation 622 corresponding to a particularcharacteristic of the sample substance 602. In particular, the modifiedelectromagnetic radiation 622 is electromagnetic radiation that hasoptically interacted with the ICE core 620, whereby an approximatemimicking of the regression vector corresponding to the characteristicof the sample substance 602 is obtained.

While FIG. 6 depicts the ICE core 620 as receiving reflectedelectromagnetic radiation from the sample substance 602, the ICE core620 may be arranged at any point along the optical train of the device600, without departing from the scope of the disclosure. For example, inone or more embodiments, the ICE core 620 (as shown in dashed lines) maybe arranged within the optical train prior to the sampling window 616and equally obtain substantially the same results. Moreover, in otherembodiments, the ICE core 620 may generate the modified electromagneticradiation 622 through reflection, instead of transmission therethrough.

The modified electromagnetic radiation 622 generated by the ICE core 620may subsequently be conveyed to a detector 624 for quantification of thesignal. The detector 624 may be any device capable of detectingelectromagnetic radiation, and may be generally characterized as anoptical transducer. In some embodiments, the detector 624 may be, but isnot limited to, a thermal detector such as a thermopile or photoacousticdetector, a semiconductor detector, a piezo-electric detector, a chargecoupled device (CCD) detector, a video or array detector, a splitdetector, a photon detector (such as a photomultiplier tube),photodiodes, combinations thereof, or the like, or other detectors knownto those skilled in the art.

In some embodiments, the detector 624 may be configured to produce anoutput signal 626 in real-time or near real-time in the form of avoltage (or current) that corresponds to the particular characteristicof interest in the sample substance 602. The voltage returned by thedetector 624 is essentially the dot product of the optical interactionof the optically interacted radiation 618 with the respective ICE core620 as a function of the concentration of the characteristic of interestof the sample substance 602. As such, the output signal 626 produced bythe detector 624 and the concentration of the characteristic may berelated, for example, directly proportional. In other embodiments,however, the relationship may correspond to a polynomial function, anexponential function, a logarithmic function, and/or a combinationthereof.

In some embodiments, the device 600 may include a second detector 628,which may be similar to the first detector 624 in that it may be anydevice capable of detecting electromagnetic radiation. The seconddetector 628 may be used to detect radiating deviations stemming fromthe electromagnetic radiation source 608. Undesirable radiatingdeviations can occur in the intensity of the electromagnetic radiation610 due to a wide variety of reasons and potentially causing variousnegative effects on the device 600. These negative effects can beparticularly detrimental for measurements taken over a period of time.In some embodiments, radiating deviations can occur as a result of abuild-up of film or material on the sampling window 616 which has theeffect of reducing the amount and quality of light ultimately reachingthe first detector 624. Without proper compensation, such radiatingdeviations could result in false readings and the output signal 626would no longer be primarily or accurately related to the characteristicof interest.

To compensate for these types of undesirable effects, the seconddetector 628 may be configured to generate a compensating signal 630generally indicative of the radiating deviations of the electromagneticradiation source 608, and thereby normalize the output signal 626generated by the first detector 624. As illustrated, the second detector628 may be configured to receive a portion of the optically interactedradiation 618 via a beamsplitter 632 in order to detect the radiatingdeviations. In other embodiments, however, the second detector 628 maybe arranged to receive electromagnetic radiation from any portion of theoptical train in the device 600 in order to detect the radiatingdeviations, without departing from the scope of the disclosure.

In some applications, the output signal 626 and the compensating signal630 may be conveyed to or otherwise received by a signal processor 634communicably coupled to both the detectors 624, 628. The signalprocessor 634 may be a computer including a processor and amachine-readable storage medium having instructions stored thereon,which, when executed by the processor 634, cause the optical computingdevice 600 to perform a number of operations, such as determining acharacteristic of interest of the sample substance 602. For instance,the concentration of each characteristic detected with the opticalcomputing device 600 can be fed into an algorithm operated by the signalprocessor 634. The algorithm can be part of an artificial neural networkconfigured to use the concentration of each detected characteristic inorder to evaluate the overall characteristic(s) or quality of the samplesubstance 602.

The signal processor 634 may also be configured to computationallycombine the compensating signal 630 with the output signal 626 in orderto normalize the output signal 626 in view of any radiating deviationsdetected by the second detector 628. In real-time or near real-time, thesignal processor 634 may be configured to provide a resulting outputsignal 636 corresponding to a concentration of the characteristic ofinterest in the sample substance 602.

Referring now to FIG. 7, with continued reference to FIG. 6, illustratedis an exemplary wellbore drilling assembly 700 that may employ theoptical computing device 600 of FIG. 6, including the ICE core 620, inorder to monitor a drilling operation, according to one or moreembodiments. The drilling assembly 700 may include a drilling platform702 that supports a derrick 704 having a traveling block 706 for raisingand lowering a drill string 708. A kelly 710 supports the drill string708 as it is lowered through a rotary bit 714. A drill bit 714 isattached to the distal end of the drill string 708 and is driven eitherby a downhole motor and/or via rotation of the drill string 708 from thewell surface. As the bit 714 rotates, it creates a borehole 716 thatpenetrates various subterranean formations 718.

A pump 720 (e.g., a mud pump) circulates drilling fluid 722 through afeed pipe 724 and to the kelly 710, which conveys the drilling fluid 722downhole through an interior conduit defined in the drill string 708 andthrough one or more orifices in the drill bit 714. The drilling fluid722 is then circulated back to the surface via an annulus 726 definedbetween the drill string 708 and the walls of the borehole 716. At thesurface, the recirculated or spent drilling fluid 722 exits the annulus726 and may be conveyed to one or more solids control equipment 728 viaan interconnecting flow line and subsequently to a retention pit 730.The drilling fluid 722 may then be recirculated back downhole via thepump 720.

A bottom hole assembly (BHA) 732 may be in in the drill string 708 at ornear the drill bit 714. The BHA 732 may include any of a number ofsensor modules, which may include formation evaluation sensors anddirectional sensors, such as measuring-while-drilling and/orlogging-while-drilling tools. The BHA 732 may further include at leastone optical computing device 734, similar to the optical computingdevice 600 of FIG. 6. The optical computing device 734 may be configuredto monitor the drilling fluid 722 within the annulus 726 as it returnsto the surface. The optical computing device 734 may include at leastone ICE core (not shown) substantially similar to the ICE cores 100, 600described above and fabricated using one of the methods 200, 500 ofFIGS. 2 and 5, respectively, as discussed above. In some embodiments,the drilling assembly 700 may further include another optical computingdevice 736 may be arranged to monitor the drilling fluid 722 as it isrecirculated or otherwise exits out of the borehole 716. The opticalcomputing device 734 may also include at least one ICE core (not shown)substantially similar to the ICE cores 100, 600 described above andfabricated using one of the methods 200, 500 of FIGS. 2 and 5,respectively, as discussed above.

While the optical computing devices 734, 736 are depicted as being usedin conjunction with a the drilling assembly 700, it will be appreciatedthat one or both of the optical computing devices 734, 736 may be usedin conjunction with several other downhole tools in obtaining a varietyof downhole measurements. For instance, the optical computing devices734, 736 may be used in conjunction with, but not limited to, a samplingtool of a wireline application, a measurement device associated withproduction tubing, etc., without departing from the scope of thedisclosure.

Embodiments disclosed herein include:

A. A method that includes providing a substrate that has at least afirst surface and a second surface opposite the first surface,depositing multiple optical thin films on the first and second surfacesof the substrate via a thin film deposition process, and therebygenerating a multilayer film stack device, cleaving the substrate toproduce at least two optical thin film stacks, and securing one or moreof the at least two optical thin film stacks to a secondary opticalelement for use as an integrated computational element (ICE).

B. A method that includes providing a substrate, depositing multipleoptical thin films on a surface of the substrate via a thin filmdeposition process and thereby generating an optical thin film stack,removing at least a portion of the substrate from the optical thin filmstack, and securing the optical thin film stack to a secondary opticalelement for use as an integrated computational element (ICE).

C. A system that includes a downhole tool extendable within a wellborepenetrating a subterranean formation, and an optical computing devicearranged on the downhole tool and configured to monitor a substancewithin the wellbore, the optical computing device including at least oneintegrated computational element (ICE) that has been fabricatedaccording to the following steps: providing a substrate that has atleast a first surface and a second surface substantially opposite thefirst surface, depositing multiple optical thin films on the first andsecond surfaces of the substrate via a thin film deposition process, andthereby generating a multilayer film stack device, and cleaving thesubstrate to produce at least two optical thin film stacks, wherein oneof the at least two optical thin film stacks is the at least one ICE.

Each of embodiments A, B, and C may have one or more of the followingadditional elements in any combination: Element 1: wherein the substrateis planar. Element 2: where the substrate is at least one of mica,pyrolitic carbon, graphite, and graphene. Element 3: wherein depositingthe multiple optical thin films on the substrate is preceded bypreparing the first and second surfaces of the substrate. Element 4:wherein preparing the first and second surfaces of the substratecomprises reducing a thickness of the substrate either chemically ormechanically. Element 5: wherein preparing the first and second surfacesof the substrate comprises chemically treating at least one of the firstand second surfaces so that it becomes more receptive to the thin filmdeposition process. Element 6: wherein the thin film deposition processis an atomic layer deposition (ALD) process, and wherein depositing themultiple optical thin films on the first and second surfaces of thesubstrate comprises suspending the substrate within an ALD reactionchamber, and sequentially growing the multiple optical thin film layerson both of the first and second surfaces of the substrate. Element 7:wherein a first optical thin film layer of the multiple optical thinfilm layers is made of a metal oxide. Element 8: further comprisingdepositing the first optical thin film layer to a thickness that isgreater than an adjacent optical thin film layer. Element 9: whereincleaving the substrate is preceded by subdividing the multilayer filmstack device into multiple optical thin film units. Element 10: whereinsecuring the one or more of the at least two optical thin film stacks tothe secondary optical element is preceded by removing the substrate fromthe one or more of the at least two optical thin film stacks. Element11: further comprising chemically removing the substrate from the one ormore of the at least two optical thin film stacks by at least one ofsubjecting the substrate to low temperature oxidation, combusting thesubstrate, and dissolving the substrate in a solvent bath. Element 12:wherein securing the one or more of the at least two optical thin filmstacks to the secondary optical element comprises at least one of usingan adhesive, sintering edges of the one or more of the at least twooptical thin film stacks, and melting a target surface of the secondaryoptical element. Element 13: wherein securing the one or more of the atleast two optical thin film stacks to the secondary optical elementcomprises chemically reacting the substrate of the one or more of the atleast two optical thin film stacks, and melting a target surface of thesecondary optical element to bond the one or more of the at least twooptical thin film stacks to the secondary optical element.

Element 14: wherein depositing the multiple optical thin films on thesubstrate is preceded by preparing the surface of the substrate eitherchemically or mechanically. Element 15: wherein securing the opticalthin film stack to the secondary optical element is preceded bysubdividing the optical thin film stack into multiple optical thin filmstacks. Element 16: wherein removing the at least a portion of thesubstrate from the optical thin film stack is preceded by securing theoptical thin film stack to the secondary optical element. Element 17:further comprising chemically reacting the substrate and thereby meltinga target surface of the secondary optical element to bond the opticalthin film stack to the secondary optical element. Element 18: whereinremoving the portion of the substrate from the optical thin film stackcomprises chemically removing the substrate from the optical thin filmstack by at least one of subjecting the substrate to low temperatureoxidation, combusting the substrate, and dissolving the substrate in asolvent bath. Element 19: wherein the secondary optical element is acomponent of an optical computing device selected from the groupconsisting of a sector of a filter wheel, a band pass filter, a lens, asurface of an optical fiber, a sampling window, a sapphire opticalelement, a non-planar optical element, and a detector. Element 20:wherein securing the optical thin film stack to the secondary opticalelement comprises at least one of using an adhesive, sintering edges ofthe optical thin film stack, and melting a target surface of thesecondary optical element. Element 21: wherein securing the optical thinfilm stack to the secondary optical element comprises chemicallyreacting the substrate of the optical thin film stack and therebymelting a target surface of the secondary optical element to bond theoptical thin film stack to the secondary optical element.

Element 22: wherein the at least one ICE is secured to a secondaryoptical element of the optical computing device, and wherein thesecondary optical element is a component selected from the groupconsisting of a sector of a filter wheel, a band pass filter, a lens, asurface of an optical fiber, a sampling window, a sapphire opticalelement, a non-planar optical element, and a detector. Element 23:wherein the downhole tool is a tool selected from the group consistingof a bottom hole assembly, a sampling tool of a wireline application,and a measurement device associated with production tubing.

Therefore, the disclosed systems and methods are well adapted to attainthe ends and advantages mentioned as well as those that are inherenttherein. The particular embodiments disclosed above are illustrativeonly, as the teachings of the present disclosure may be modified andpracticed in different but equivalent manners apparent to those skilledin the art having the benefit of the teachings herein. Furthermore, nolimitations are intended to the details of construction or design hereinshown, other than as described in the claims below. It is thereforeevident that the particular illustrative embodiments disclosed above maybe altered, combined, or modified and all such variations are consideredwithin the scope of the present disclosure. The systems and methodsillustratively disclosed herein may suitably be practiced in the absenceof any element that is not specifically disclosed herein and/or anyoptional element disclosed herein. While compositions and methods aredescribed in terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps. Allnumbers and ranges disclosed above may vary by some amount. Whenever anumerical range with a lower limit and an upper limit is disclosed, anynumber and any included range falling within the range is specificallydisclosed. In particular, every range of values (of the form, “fromabout a to about b,” or, equivalently, “from approximately a to b,” or,equivalently, “from approximately a-b”) disclosed herein is to beunderstood to set forth every number and range encompassed within thebroader range of values. Also, the terms in the claims have their plain,ordinary meaning unless otherwise explicitly and clearly defined by thepatentee. Moreover, the indefinite articles “a” or “an,” as used in theclaims, are defined herein to mean one or more than one of the elementthat it introduces. If there is any conflict in the usages of a word orterm in this specification and one or more patent or other documentsthat may be incorporated herein by reference, the definitions that areconsistent with this specification should be adopted.

As used herein, the phrase “at least one of” preceding a series ofitems, with the terms “and” or “or” to separate any of the items,modifies the list as a whole, rather than each member of the list (i.e.,each item). The phrase “at least one of” does not require selection ofat least one item; rather, the phrase allows a meaning that includes atleast one of any one of the items, and/or at least one of anycombination of the items, and/or at least one of each of the items. Byway of example, the phrases “at least one of A, B, and C” or “at leastone of A, B, or C” each refer to only A, only B, or only C; anycombination of A, B, and C; and/or at least one of each of A, B, and C.

What is claimed is:
 1. A method, comprising: providing a substrate that has at least a first surface and a second surface substantially opposite the first surface; depositing multiple optical thin films on the first surface and the second surface of the substrate via a thin film deposition process, wherein each of the multiple optical thin films is deposited simultaneously on the first surface and on the second surface of the substrate; cleaving the substrate with a planar cut, the planar cut parallel to the first surface and the second surface, to produce at least two optical thin film stacks and thereby generating at least two multilayer film stack devices comprising a first optical thin film stack formed on the first surface and a second optical thin film stack formed on the second surface, wherein each layer in the first optical thin film stack mirrors a corresponding layer in the second optical thin film stack, and wherein each of the at least two multilayer film stack devices is suitable for use in a same optical computing device; and securing one or more of the at least two optical thin film stacks to a secondary optical element for use as an integrated computational element (ICE).
 2. The method of claim 1, wherein the substrate is planar.
 3. The method of claim 2, where the substrate is at least one of mica, pyrolitic carbon, graphite, and graphene.
 4. The method of claim 1, wherein depositing the multiple optical thin films on the substrate is preceded by preparing the first surface and the second surface of the substrate.
 5. The method of claim 4, wherein preparing the first surface and the second surface of the substrate comprises reducing a thickness of the substrate either chemically or mechanically.
 6. The method of claim 4, wherein preparing the first surface and the second surface of the substrate comprises chemically treating at least one of the first surface and the second surface so that it becomes more receptive to the thin film deposition process.
 7. The method of claim 1, wherein the thin film deposition process is an atomic layer deposition (ALD) process, and wherein depositing the multiple optical thin films on the first surface and the second surface of the substrate comprises: suspending the substrate within an ALD reaction chamber; and sequentially depositing the multiple optical thin films on both of the first surface and the second surface of the substrate.
 8. The method of claim 7, wherein a first optical thin film of the multiple optical thin films is made of a metal oxide.
 9. The method of claim 8, further comprising depositing a first optical thin film layer to a thickness that is greater than an adjacent optical thin film layer.
 10. The method of claim 1, wherein cleaving the substrate is preceded by subdividing the multiple optical thin films into multiple optical thin film units.
 11. The method of claim 1, wherein securing the one or more of the at least two optical thin film stacks to the secondary optical element is preceded by removing the substrate from the one or more of the at least two optical thin film stacks.
 12. The method of claim 11, further comprising chemically removing the substrate from the one or more of the at least two optical thin film stacks by at least one of subjecting the substrate to low temperature oxidation, combusting the substrate, and dissolving the substrate in a solvent bath.
 13. The method of claim 1, wherein securing the one or more of the at least two optical thin film stacks to the secondary optical element comprises at least one of using an adhesive, sintering edges of the one or more of the at least two optical thin film stacks, and melting a target surface of the secondary optical element.
 14. The method of claim 1, wherein securing the one or more of the at least two optical thin film stacks to the secondary optical element comprises: chemically reacting the substrate of the one or more of the at least two optical thin film stacks; and melting a target surface of the secondary optical element to bond the one or more of the at least two optical thin film stacks to the secondary optical element. 